A hierarchical control strategy for the autonomous navigation of a ducted fan flying robot

This paper describes a control strategy to stabilize the position of a vertical takeoff and landing (VTOL) unmanned aerial vehicle (UAV) in wind gusts. The proposed approach takes advantage of the cascade structure of the system to design a hierarchical controller. The idea is to separate the controller in a high level controller devoted to position control and a low level controller devoted to stabilization and attitude control. Both controllers are designed by means of backstepping techniques that allow the stabilization of the vehicle´s position while on-line estimation of the unknown aerodynamic forces. The global stability of the connected system is proven, and simulations as well as experimental results are presented